Biology subjects

Liu, F.

Publications and source records attributed to Liu, F..

At least 271 records · Page 15Linked to original sources

bioRxiv2021

C-type natriuretic peptide facilitates autonomic Ca2+ entry in growth plate chondrocytes for stimulating bone growth

The growth plates are cartilage tissues found at both ends of developing bones, and vital proliferation and differentiation of growth plate chondrocytes are primarily responsible for bone growth. C-type natriuretic peptide (CNP) stimulates bone growth by activating natriuretic peptide receptor 2 (NPR2) which is equipped with guanylate cyclase on the cytoplasmic side, but its signaling pathway is unclear in growth plate chondrocytes. We previously reported that transient receptor potential melastatin-like 7 (TRPM7) channels mediate intermissive Ca2+ influx in growth plate chondrocytes, leading to activation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) for promoting bone growth. In this report, we provide experimental evidence indicating a functional link between CNP and TRPM7 channels. Our pharmacological data suggest that CNP-evoked NPR2 activation elevates cellular cGMP content and stimulates big-conductance Ca2+-dependent K+ (BK) channels as a substrate for cGMP-dependent protein kinase (PKG). BK channel-induced hyperpolarization likely enhances the driving force of TRPM7-mediated Ca2+ entry and seems to accordingly activate CaMKII. Indeed, ex vivo organ culture analysis indicates that CNP-facilitated bone growth is abolished by chondrocyte-specific Trpm7 gene ablation. The defined CNP signaling pathway, the NPR2-PKG-BK channel-TRPM7 channel-CaMKII axis, likely pinpoints promising target proteins for developing new therapeutic treatments for divergent growth disorders.

cell biology↗

bioRxiv2021

The chromatin-remodeling enzyme Smarca5 regulates erythrocyte aggregation via Keap1-Nrf2 signaling

Although thrombosis has been extensively studied using various animal models, however, our understanding of the underlying mechanism remains elusive. Here, using zebrafish model, we demonstrated that smarca5-deficient red blood cells (RBCs) formed blood clots in the caudal vein plexus that mimics venous thrombosis. We further used the anti-thrombosis drugs to treat smarca5zko1049a embryos and found that a thrombin inhibitor, argatroban, partially prevented blood clot formation in smarca5zko1049a. To explore the regulatory mechanism of smarca5 in RBC homeostasis, we profiled the chromatin accessibility landscape and transcriptome features in RBCs from smarca5zko1049a and their siblings and found that both the chromatin accessibility at the keap1a promoter and expression of keap1a were decreased. Keap1 is a suppressor protein of Nrf2, which is a major regulator of oxidative responses. We further identified that the expression of hmox1a, a downstream target of Keap1-Nrf2 signaling pathway, was markedly increased upon smarca5 deletion. Importantly, overexpression of keap1a or knockdown of hmox1a partially rescued the blood clot formation, suggesting that the disrupted Keap1-Nrf2 signaling is responsible for the venous thrombosis-like phenotypes in smarca5 mutants. Together, our study using zebrafish smarca5 mutants not only characterizes a novel role for smarca5 in blood clot formation, but also provides a new venous thrombosis animal model to support drug screening and pre-clinical therapeutic assessments to treat thrombosis.

developmental biology↗

bioRxiv2021

The exosomes derived from urine of premature infants target MAPK8 via miR-30a-5p to protect cisplatin-induced acute kidney injury in mice

AimAcute kidney injury (AKI), a global public health issue, not only causes millions of deaths every year, but is also a susceptible factor for chronic kidney disease (CKD). Nephrotoxic drugs are an important cause of AKI. There is still a lack of effective and satisfactory prevention method in clinical practice. This study investigated the protective effect of the exosomes derived from urine of premature infants on cisplatin-induced acute kidney injury. MethodsIsolation of exosomes from fresh urine of premature infants: The characteristics of exosomes were determined by flow cytometry, transmission electron microscopy and Western blotting. A C57BL/6 mice model of cisplatin-induced acute kidney injury was established. The mice in the experimental group were given 100ug exosomes dissolved in 200ul solution. The mice in the control group were given normal saline (200ul). These treatments were performed 24 hours after AKI was induced by intraperitoneal injection of cisplatin. To evaluate renal function, blood was drawn 24 hours after AKI model was established and serum creatinine (sCr) was measured. The mice were euthanized 72 hours after exosome treatment. The kidneys were collected for pathological examination, RNA and protein extraction, and the evaluation of renal tubular damage and apoptosis. In the in-vitro experiment, human renal cortex/proximal tubular cells (HK2) was induced by cisplatin to assess the protective ability of the exosomes derived from urine of premature infants. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western Blotting were used to evaluate the effect of exosomes treatment on the apoptosis of HK2 cells induced by cisplatin. Exosome microRNA sequencing technology and bioinformatics analysis method were applied to investigate the miRNAs enriched in exosomes and their target genes. The dual luciferase gene reporter system was used to detect the interaction of target genes. ResultsTreatment of exosomes derived from urine of premature infants could decrease the level of serum creatinine and the apoptosis of renal tubular cell, inhibit the infiltration of inflammatory cell, protect mice from acute kidney injury induced by cisplatin and reduce mortality. In addition, miR-30a-5p was the most abundant miRNA in the exosomes derived from urine of premature infants. It protected HK2 cells from cisplatin-induced apoptosis by targeting and down-regulating the 3UTR of mitogen-activated protein kinases (MAPK8) mRNA. ConclusionsAccording to our results, the exosomes derived from urine of premature infants alleviated cisplatin-induced acute kidney injury in mice and inhibited the apoptosis of human proximal tubular cells (HK2) induced by cisplatin in vitro. MiR-30a-5p in exosomes inhibited cisplatin-induced MAPK activation, ameliorated apoptosis, and protected renal function. The exosomes derived from urine of premature infants provided a promising acellular therapy for AKI.

molecular biology↗

bioRxiv2021

Target Enrichment Enhances the Sensitivity of Sanger Sequencing for BRAF V600 Mutation Detection

BRAF is a serine/threonine protein kinase whose mutations lead to unregulated cell growth and cause different types of cancers. Since V600E is a major BRAF mutation and V600E detection as a companion diagnostic test (CDx) is stipulated in the labeling of the BRAF V600 inhibitors. Traditional Sanger sequencing cannot accurately detect mutations lower than 15% variant allele frequency (VAF) due to its limited sensitivity. Here we applied our patented XNA molecular clamping technology to modify Sanger sequencing template preparation by enriching the mutation population. We found that the use of our mutation-enriched template enhanced the analytical sensitivity of Sanger sequencing to 0.04% VAF. The method is verified to detect V600E, V600K, and V600R mutants and is validated for the known BRAF mutation status in clinical samples. Our streamlined protocol can be used for easy validation of the highly sensitive target-enrichment method for detecting BRAF V600 mutations using Sanger sequencing in clinical labs. In addition to BRAF V600 mutations, this method can be extended to the detection of other clinically important actionable mutations for cancer diagnostics.

molecular biology↗

bioRxiv2021

High-throughput production of functional prototissues capable of producing NO for vasodilation

Bottom-up synthesis of prototissues helps us to understand the internal cellular communications in the natural tissues and their functions, as well as to improve or repair the damaged tissues. The existed prototissues are rarely used to improve the function of living tissues. We demonstrated a methodology to produce spatially programmable prototissues based on the magneto-Archimedes effect in a high-throughput manner. More than 2000 prototissues are produced once within 2 hours. Two-component and three-component spatial coded prototissues are fabricated by varying the addition giant unilamellar vesicles (GUVs) order/number, and the magnetic field distributions. Two-step and three-step signal communications in the prototissues are realized using cascade enzyme reactions. More importantly, the two-component prototissues capable of producing nitric oxide (NO) cause vasodilation of rat blood vessels in the presence of glucose and hydroxyurea. The tension force decreases 2.59 g, meanwhile the blood vessel relaxation is of 31.2%. Our works pave the path to fabricate complicated programmable prototissues, and hold great potential in tissue transplantation in the biomedical field.

bioengineering↗

bioRxiv2021

ENGINEERING, DECODING AND SYSTEMS-LEVEL CHARACTERIZATION OF CHIMPANZEE CYTOMEGALOVIRUS

The chimpanzee cytomegalovirus (CCMV) is the closest relative of human CMV (HCMV). Because of the high conservation between these two species and the ability of human cells to fully support CCMV replication, CCMV holds great potential as a model system for HCMV. To make the CCMV genome available for precise and rapid gene manipulation techniques, we captured the genomic DNA of CCMV strain Heberling as a bacterial artificial chromosome (BAC). Selected BAC clones were reconstituted to infectious viruses, growing to similar high titers as parental CCMV. DNA sequencing confirmed the integrity of our clones and led to the identification of two polymorphic loci within the CCMV genome. To re-evaluate the CCMV coding potential, we analyzed the transcriptome and proteome of infected cells and identified several novel ORFs, splice variants, and regulatory RNAs. We further characterized the dynamics of CCMV gene expression and found that viral proteins cluster into five distinct temporal classes. In addition, our datasets revealed that the host response to CCMV infection and the de-regulation of cellular pathways are in line with known hallmarks of HCMV infection. In a first functional experiment, we investigated a proposed frameshift mutation in UL128 that was suspected to restrict CCMVs cell tropism. In fact, repair of this frameshift re-established productive CCMV infection in endothelial and epithelial cells, expanding the options of CCMV as an infection model. Thus, BAC-cloned CCMV can serve as a powerful tool for systematic approaches in comparative functional genomics, exploiting the close phylogenetic relationship between CCMV and HCMV.

microbiology↗

bioRxiv2021

LENG8 regulation of mRNA processing, is responsible for the control of mitochondrial activity

The processing of mRNA is essential for the maintenance of cellular and tissue homeostasis. However, the precise regulation of this process in mammalian cells, remains largely unknown. Here we have found that LENG8 represents the mammalian orthologue of the yeast mRNA processing factor Thp3 and Sac3. We go on to demonstrate that LENG8 binds to mRNAs, associates with components of mRNA processing machinery (the TREX complex) and contributes to mRNA nuclear export to the cytoplasm. Loss of LENG8, leads to aberrant accumulation of poly (A)+ RNA in the nucleus, in both Hela cells and murine fibroblasts. Furthermore, the precipitation of LENG8, is associated with an enrichment of both mRNAs and lncRNAs, and approximately half of these are also bound by the TREX component, THOC1. However, LENG8 preferentially binds mRNAs encoding for mitochondrial proteins and depletion of this processing factor, causes a dramatic breakdown in mitochondrial ultrastructure and a reduction in mitochondrial respiratory activity. Conditional deletion of Leng8 in mouse adipose tissues lead to a decreased body weight, and increased adipose thermogenesis. Our work has found an evolutionarily conserved mRNA processing factor that can control mitochondrial activity.

cell biology↗

bioRxiv2021

A Lethal Genetic Incompatibility between Naturally Hybridizing Species in Mitochondrial Complex I

The evolution of reproductive barriers is the first step in the formation of new species and can help us understand the diversification of life on Earth. These reproductive barriers often take the form of "hybrid incompatibilities," where alleles derived from two different species no longer interact properly in hybrids. Theory predicts that hybrid incompatibilities may be more likely to arise at rapidly evolving genes and that incompatibilities involving multiple genes should be common, but there has been sparse empirical data to evaluate these predictions. Here, we describe a mitonuclear incompatibility involving three genes in physical contact within respiratory Complex I in naturally hybridizing swordtail fish species. Individuals homozygous for specific mismatched protein combinations fail to complete embryonic development or die as juveniles, while those heterozygous for the incompatibility have reduced function of Complex I and unbalanced representation of parental alleles in the mitochondrial proteome. We find that the impacts of different genetic interactions on survival are non-additive, highlighting subtle complexity in the genetic architecture of hybrid incompatibilities. We document the evolutionary history of the genes involved, showing for the first time that an incompatibility has been transferred between species via hybridization. This work thus provides the first glimpse into the genetic architecture, physiological impacts, and evolutionary origin of a complex incompatibility impacting naturally hybridizing species.

evolutionary biology↗

bioRxiv2021

Cell-type specific transcriptional adaptations of nucleus accumbens interneurons to amphetamine

Parvalbumin-expressing (PV+) interneurons of the nucleus accumbens (NAc) play an essential role in the addictive-like behaviors induced by psychostimulant exposure. To identify molecular mechanisms of PV+ neuron plasticity, we isolated interneuron nuclei from the NAc of male and female mice following acute or repeated exposure to amphetamine (AMPH) and sequenced for cell type-specific RNA expression and chromatin accessibility. AMPH regulated the transcription of hundreds of genes in PV+ interneurons, and this program was largely distinct from that regulated in other NAc GABAergic neurons. Chromatin accessibility at enhancers predicted cell-type specific gene regulation, identifying transcriptional mechanisms of differential AMPH responses. Finally, we observed dysregulation of multiple PV-specific, AMPH-regulated genes in an Mecp2 mutant mouse strain that shows heightened behavioral sensitivity to psychostimulants, suggesting the functional importance of this transcriptional program. Together these data provide novel insight into the cell-type specific programs of transcriptional plasticity in NAc neurons that underlie addictive-like behaviors.

neuroscience↗

bioRxiv2021

Discrete Roles of the Ir76b Ionotropic Co-Receptor Impact Olfaction, Blood Feeding, and Mating in the Malaria Vector Mosquito Anopheles coluzzii

Anopheline mosquitoes rely on their highly sensitive chemosensory apparatus to detect diverse chemical stimuli that drive the host-seeking and blood-feeding behaviors required to vector pathogens for malaria and other diseases. This process incorporates a variety of chemosensory receptors and transduction pathways. We have used advanced in vivo gene-editing and -labelling approaches to localize and functionally characterize the ionotropic co-receptor AcIr76b in the malaria mosquito Anopheles coluzzii, where it impacts both olfactory and gustatory systems. AcIr76b has a broad expression pattern in female adult antennal grooved pegs, T1 and T2 sensilla on the labellum, stylets, and tarsi, as well as the larval sensory peg. AcIr76b is co-localized with the Orco odorant receptor (OR) co-receptor in a subset of cells across the female antennae and labella. In contrast to Orco and Ir8a, chemosensory co-receptors that appear essential for the activity of their respective sets of chemosensory neurons in mosquitoes, AcIr76b-/- mutants maintain wild-type peripheral responses to volatile amines on the adult palps, labellum, and the larval sensory cone. Interestingly, AcIr76b-/- mutants display significantly increased responses to amines in antennal grooved peg sensilla while coeloconic sensilla reveal significant deficits in responses to several acids and amines. Behaviorally, AcIr76b mutants manifest significantly female-specific insemination deficits and, although AcIr76b-/- mutant females are able to locate, alight, and probe artificial blood hosts, they are incapable of blood feeding successfully. Taken together, our study reveals a multi-dimensional functionality of Ir76b in Anopheline olfactory and gustatory pathways that directly impacts the vectorial capacity of these mosquitoes. SummaryChemosensory receptors play crucial roles across mosquito lifecycles where they often form functional complexes that require cognate co-receptors. To better understand mosquito chemosensory pathways in the malaria vector mosquito An. coluzzii we have utilized advanced gene editing approaches to localize and functionally characterize the ionotropic receptor co-receptor AcIr76b. Expression of AcIr76b was observed in antennal grooved pegs and other accessory olfactory appendages. Mutagenesis of AcIr76b uncovers both reduced and elevated neuronal responses to amines, which suggests a role in response modulation. In addition to olfactory phenotypes, AcIr76b mutants display significantly impaired mating and blood feeding capabilities. Our data reveals discrete roles of AcIr76b across olfactory and gustatory pathways and shed lights on the potential molecular target for vector control strategies.

neuroscience↗

bioRxiv2021

Zebrafish Cre/lox regulated UFlip alleles generated by CRISPR/Cas targeted integration provide cell-type specific conditional gene inactivation

The ability to regulate gene activity spatially and temporally is essential to investigate cell type specific gene function during development and in postembryonic processes and disease models. The Cre/lox system has been widely used for performing cell and tissue-specific conditional analysis of gene function in zebrafish, but simple and efficient methods for isolation of stable, Cre/lox regulated alleles are lacking. Here we applied our GeneWeld CRISPR/Cas9 short homology-directed targeted integration strategy to generate floxed conditional alleles that provide robust gene knockdown and strong loss of function phenotypes. A universal targeting vector, UFlip, with sites for cloning short 24-48 bp homology arms flanking a floxed mRFP gene trap plus secondary reporter cassette, was integrated into an intron in hdac1, rbbp4, and rb1. Active, gene off orientation hdac1-UFlip-Off and rb1-UFlip-Off integration alleles result in >99% reduction of gene expression in homozygotes and recapitulate known indel loss of function phenotypes. Passive, gene on orientation rbbp4-UFlip-On and rb1-UFlip-On integration alleles do not cause phenotypes in trans-heterozygous combination with an indel mutation. Cre recombinase injection leads to recombination at alternating pairs of loxP and lox2272 sites, inverting and locking the cassette into the active, gene off orientation, and the expected mutant phenotypes. In combination with our endogenous neural progenitor Cre drivers we demonstrate rbbp4-UFlip-On and rb1-UFlip-On gene inactivation phenotypes can be restricted to specific neural cell populations. Replacement of the UFlip mRFP primary reporter gene trap with a 2A-RFP in rbbp4-UFlip-Off, or 2A-KalTA4 in rb1-UFlip-Off, shows strong RFP expression in wild type or UAS:RFP injected embryos, respectively. Together these results validate a simplified approach for efficient isolation of highly mutagenic Cre/lox responsive conditional gene alleles to advance zebrafish Cre recombinase genetics.

genetics↗

bioRxiv2021

Reconstitution of the DTX3L-PARP9 complex reveals determinants for high affinity heterodimer formation and enzymatic function

Ubiquitination and ADP-ribosylation are post-translational modifications that play major roles in pathways like DNA damage response and infection, making them attractive targets for therapeutic intervention. DTX3L, an E3 ubiquitin ligase, forms a heterodimer with PARP9. The complex has ubiquitin ligase activity and also ADP-ribosylates the C-terminus of ubiquitin on Gly76. NAD+-dependent ADP-ribosylation of ubiquitin by DTX3L-PARP9 prevents ubiquitin from conjugating to protein substrates. By using individually produced proteins, we have studied the interaction between DTX3L and PARP9. We identify that the D3 domain (230 - 510) of DTX3L mediates interaction with PARP9 with nanomolar affinity and an apparent 1:1 stoichiometry. Our results also suggest the formation of a higher molecular weight oligomer mediated by the N-terminus of DTX3L (1-200). Furthermore, we show that ADP-ribosylation of ubiquitin at Gly76 is a reversible modification that can be removed by several macrodomain-type hydrolases. Our study provides a framework to understand how DTX3L-PARP9 mediates ADP-ribosylation and ubiquitination in an inter-regulatory manner.

biochemistry↗

bioRxiv2021

Effect of straw incorporation and nitrification inhibitor on nitrous oxide emission in various cropland soils and its microbial mechanism

Nitrification inhibitor and straw incorporation are widely used to improve crop nitrogen use efficiency in agricultural soil, but their effects on nitrous oxide (N2O) emission across different soil types and the microbial mechanisms remain less understood. In this study, we used controlled experiment and DNA-based molecular analysis to study how nitrification inhibitor (dicyandiamide, DCD) and straw incorporation affect soil nitrogen balance, N2O emission and microbial nitrifiers/denitrifers in three distinct agricultural soils (the black, fluvo-aquic and red soils) across China. Both DCD and straw incorporation improved nitrogen balance by increasing NH4+ and decreasing NO3- in all soils. DCD tended to decrease N2O emission from all soils especially the fluvo-aquic one, while straw incorporation reduced N2O emission only in the fluvo-aquic soil but increased N2O emission in the other two especially the red soil (by [~]600%). T-RFLP analysis revealed that the denitriers community structure are distinct among the three soils but was not strongly affected by DCD or straw incorporation. qPCR analysis revealed that DCD or straw incorporation had no significant effect on nitrifier abundance but increased nitrous oxide reductase nosZ gene abundance in the black/fluvo-aquic soil rather than the red soil. Structural equational modelling further confirmed that, when accounting for treatments and soil properties, nosZ gene abundance is the only biological factor significantly determined N2O emission in different soil types. Taken together, our work advanced the knowledge on the agricultural practices and N2O emission in cropland soils, suggesting that straw incorporation may not be a good choice for the red and black soil areas; management practices should be used as per soil type to balance between nitrogen use efficiency and N2O emission.

ecology↗

bioRxiv2021

Knocking-out the human face genes TBX15 and PAX1 in mice alters facial and other physical morphology

DNA variants in or closed to the human TBX15 and PAX1 genes have been repeatedly associated with facial morphology in independent genome-wide association studies, while their functional roles in determining facial morphology remains to be understood. We generated Tbx15 knockout (Tbx15-/-) and Pax1 knockout (Pax1-/-) mice by applying the one-step CRISPR/Cas9 method. A total of 75 adult mice were used for subsequent phenotype analysis, including 38 Tbx15 mice (10 homozygous Tbx15-/-, 18 heterozygous Tbx15+/-, 10 wild-type WT) and 37 Pax1 mice (12 homozygous Pax1-/-, 15 heterozygous Pax1+/-, 10 WT mice). Facial and other physical morphological phenotypes were obtained from three-dimensional (3D) images acquired with the HandySCAN BLACK scanner. Compared to WT mice, the Tbx15-/- mutant mice had significantly shorter faces (P=1.08E-8, R2=0.61) and their ears were in a significantly lower position (P=3.54E-8, R2=0.62) manifesting an "ear dropping" characteristic. Besides these face alternations, Tbx15-/- mutant mice displayed significantly lower weight as well as shorter body and limb length. Pax1-/- mutant mice showed significantly longer noses (P=1.14E-5, R2=0.46) relative to WT mice, but otherwise displayed less obvious morphological alterations than Tbx15-/- mutant mice did. Because the Tbx15 and Pax1 effects on facial morphology we revealed here in mice are largely consistent with previously reported TBX15 and PAX1 face associations in humans, we suggest that the functional role these two genes play on determining the face of mice is similar to the functional impact their human homologues have on the face of humans. Author SummarySeveral independent genome-wide association studies (GWASs) on human facial morphology highlighted DNA variants in or closed to TBX15 and PAX1 with genome-wide significant association with human facial phenotypes. However, direct evidence on the functional involvement if these genes in the development and determination of facial morphology has not been established as of yet. In the current study, our in vivo gene editing experiments in mice for two well-replicated human face TBX15 and PAX1 genes provide novel evidence on the functional involvement of these two genes in facial and other physical morphology in mice, at least. Tbx15-/- mice showed a shortened facial length and manifesting an ear dropping characteristic, Pax1-/- mice showed an increased nose length. Our geometric morphometrics analysis further indicate that there are significant facial morphology differences between groups (Tbx15-/-and Tbx15+/-, Tbx15-/- and Tbx15+/+, Tbx15+/- and Tbx15+/+, Pax1-/- and Pax1+/+). We provide the first direct functional evidence that two well-known and replicated human face genes, Tbx15 and Pax1, impact facial and other body morphology in mice. The general agreement between our findings in knock-out mice with those from previous GWASs suggests that the functional evidence we established here in mice may also be relevant in humans.

genetics↗

bioRxiv2021

TranSyT, the Transport Systems Tracker

The importance and rate of development of genome-scale metabolic models have been growing for the last years, increasing the demand for software solutions that automate several steps of this process. However, since TRIAGEs release, software development for automatic integration of transport reactions into models has stalled. Here we present the Transport Systems Tracker (TranSyT), the next iteration of TRIAGE. Unlike its predecessor, TranSyT does not rely on manual curation to expand its internal database, derived from highly-curated records retrieved from the Transporters Classification Database and complemented with information from other data sources. TranSyT compiles information regarding transporters families, transport proteins, and derives reactions into its internal database, making it available for rapid annotation of complete genomes. All transport reactions have GPR associations and can be exported with identifiers from four different metabolite databases. TranSyT is currently available as a plugin for merlin v4.0 and an app for KBase.

bioinformatics↗

bioRxiv2021

Ultrapotent SARS-CoV-2 neutralizing antibodies with protective efficacy against newly emerged mutational variants

Accumulating mutations in the SARS-CoV-2 Spike (S) protein can increase the possibility of immune escape, challenging the present COVID-19 prophylaxis and clinical interventions. Here, 3 receptor binding domain (RBD) specific monoclonal antibodies (mAbs), 58G6, 510A5 and 13G9, with high neutralizing potency blocking authentic SARS-CoV-2 virus displayed remarkable efficacy against authentic B.1.351 virus. Each of these 3 mAbs in combination with one neutralizing Ab recognizing non-competing epitope exhibited synergistic effect against authentic SARS-CoV-2 virus. Surprisingly, structural analysis revealed that 58G6 and 13G9, encoded by the IGHV1-58 and the IGKV3-20 germline genes, both recognized the steric region S470-495 on the RBD, overlapping the E484K mutation presented in B.1.351. Also, 58G6 directly bound to another region S450-458 in the RBD. Significantly, 58G6 and 510A5 both demonstrated prophylactic efficacy against authentic SARS-CoV-2 and B.1.351 viruses in the transgenic mice expressing human ACE2 (hACE2), protecting weight loss and reducing virus loads. These 2 ultrapotent neutralizing Abs can be promising candidates to fulfill the urgent needs for the prolonged COVID-19 pandemic.

immunology↗

bioRxiv2021

Host poly(A) polymerases PAPD5 and PAPD7 provide two layers of protection that ensure the integrity and stability of hepatitis B virus RNA

Noncanonical poly(A) polymerases PAPD5 and PAPD7 (PAPD5/7) stabilize HBV RNA via the interaction with the viral post-transcriptional regulatory element (PRE), representing new antiviral targets to control HBV RNA metabolism, HBsAg production and viral replication. Inhibitors targeting these proteins are being developed as antiviral therapies, therefore it is important to understand how PAPD5/7 coordinate to stabilize HBV RNA. Here, we utilized a potent small-molecule AB-452 as a chemical probe, along with genetic analyses to dissect the individual roles of PAPD5/7 in HBV RNA stability. AB-452 inhibits PAPD5/7 enzymatic activities and reduces HBsAg both in vitro (EC50 ranged from 1.4 to 6.8 nM) and in vivo by 0.93 log10. Our genetic studies demonstrate that the stem-loop alpha sequence within PRE is essential for both maintaining HBV poly(A) tail integrity and determining sensitivity towards the inhibitory effect of AB-452. Although neither single knock-out (KO) of PAPD5 nor PAPD7 reduces HBsAg RNA and protein production, PAPD5 KO does impair poly(A) tail integrity and confers partial resistance to AB-452. In contrast, PAPD7 KO could not result in any measurable phenotypic changes, but displays a similar antiviral effect as AB-452 treatment when PAPD5 is depleted simultaneously. PAPD5/7 double KO confers complete resistance to AB-452 treatment. Our results thus indicate that PAPD5 plays a dominant role in stabilizing viral RNA by protecting the integrity of its poly(A) tail, while PAPD7 serves as a second line of protection. These findings inform PAPD5 targeted therapeutic strategies and open avenues for further investigating PAPD5/7 in HBV replication. ImportanceChronic hepatitis B affects more than 250 million patients and is a major public health concern worldwide. HBsAg plays a central role in maintaining HBV persistence and as such, therapies reducing HBsAg have been extensively investigated. PAPD5/7 targeting inhibitors, with oral bioavailability, represent an opportunity to reduce both HBV RNA and HBsAg. Here we uncover that the SL sequence is required for HBV poly(A) tail integrity and RNA stability, and that the antiviral activity of AB-452 mimics the SL mutants. Although PAPD5 and PAPD7 regulate HBV RNA stability, it remains unclear how they coordinate in stabilizing HBV RNA. Based on our studies, PAPD5 plays a dominant role to stabilize viral RNA by protecting the integrity of its poly(A) tail, while PAPD7 serves as a backup protection mechanism. Our studies may point out a direction towards developing PAPD5-selective inhibitors that could be used effectively to treat chronic hepatitis B.

microbiology↗

bioRxiv2021

Two interacting transcriptional coactivators cooperatively control plant immune responses

The phytohormone salicylic acid (SA) plays a pivotal role in plant defense against biotrophic and hemibiotrophic pathogens. Genetic studies have identified NPR1 and EDS1 as two central hubs in plant local and systemic immunity. However, it is unclear how NPR1 orchestrates gene regulation and whether EDS1 directly participates in transcriptional reprogramming. Here we show that NPR1 and EDS1 synergistically activate Pathogenesis-Related (PR) genes and plant defenses by forming a protein complex and co-opting with Mediator. In particular, we discover that EDS1 functions as an autonomous transcriptional coactivator with intrinsic transactivation domains and physically interacts with the CDK8 subunit of Mediator. Upon SA induction, EDS1 is directly recruited by NPR1 onto the PR1 promoter via physical NPR1-EDS1 interactions, thereby potentiating PR1 activation. We further demonstrate that EDS1 stabilizes NPR1 protein and NPR1 transcriptionally upregulates EDS1 in plant-pathogen interactions. Our results reveal an elegant interplay of key coactivators with Mediator and elucidate novel molecular mechanisms for activating transcription during immune responses.

plant biology↗